dht20: add I2C driver for DHT20 temperature and humidity sensor

dht20/dht20.go

@@ -0,0 +1,103 @@
+// Package dht20 implements a driver for the DHT20 temperature and humidity sensor.
+//
+// Datasheet: https://cdn-shop.adafruit.com/product-files/5183/5193_DHT20.pdf
+
+package dht20
+
+import (
+	"time"
+
+	"tinygo.org/x/drivers"
+)
+
+// Device wraps an I2C connection to a DHT20 device.
+type Device struct {
+	bus            drivers.I2C
+	Address        uint16
+	data           [8]uint8
+	temperature    float32
+	humidity       float32
+	prevAccessTime time.Time
+}
+
+// New creates a new DHT20 connection. The I2C bus must already be
+// configured.
+//
+// This function only creates the Device object, it does not touch the device.
+func New(bus drivers.I2C) Device {
+	return Device{
+		bus:     bus,
+		Address: defaultAddress, // Using the address defined in registers.go
+	}
+}
+
+// Configure sets up the device for communication and initializes the registers if needed.
+func (d *Device) Configure() {
+	// Get the status word
+	d.data[0] = 0x71
+	d.bus.Tx(d.Address, d.data[:1], d.data[:1])
+	if d.data[0] != 0x18 {
+		// Initialize registers
+		d.initRegisters()
+	}
+	// Set the previous access time to the current time
+	d.prevAccessTime = time.Now()
+}
+
+// initRegisters initializes the registers 0x1B, 0x1C, and 0x1E to 0x00.
+func (d *Device) initRegisters() {
+	// Initialize register 0x1B
+	d.data[0] = 0x1B
+	d.data[1] = 0x00
+	d.bus.Tx(d.Address, d.data[:2], nil)
+
+	// Initialize register 0x1C
+	d.data[0] = 0x1C
+	d.data[1] = 0x00
+	d.bus.Tx(d.Address, d.data[:2], nil)
+
+	// Initialize register 0x1E
+	d.data[0] = 0x1E
+	d.data[1] = 0x00
+	d.bus.Tx(d.Address, d.data[:2], nil)
+}
+
+// Update reads data from the sensor and updates the temperature and humidity values.
+func (d *Device) Update(which drivers.Measurement) error {
+	// Check if 80ms have passed since the last access
+	if d.prevAccessTime.Add(80 * time.Millisecond).Before(time.Now()) {
+		// Check the status word Bit[7]
+		d.data[0] = 0x71
+		d.bus.Tx(d.Address, d.data[:1], d.data[:1])
+		if (d.data[0] & 0x80) == 0 {
+			// Read 7 bytes of data from the sensor
+			d.bus.Tx(d.Address, nil, d.data[:7])
+			rawHumidity := uint32(d.data[1])<<12 | uint32(d.data[2])<<4 | uint32(d.data[3])>>4
+			rawTemperature := uint32(d.data[3]&0x0F)<<16 | uint32(d.data[4])<<8 | uint32(d.data[5])
+
+			// Convert raw values to human-readable values
+			d.humidity = float32(rawHumidity) / 1048576.0 * 100
+			d.temperature = float32(rawTemperature)/1048576.0*200 - 50
+
+			// Trigger the next measurement
+			d.data[0] = 0xAC
+			d.data[1] = 0x33
+			d.data[2] = 0x00
+			d.bus.Tx(d.Address, d.data[:3], nil)
+
+			// Update the previous access time to the current time
+			d.prevAccessTime = time.Now()
+		}
+	}
+	return nil
+}
+
+// Temperature returns the last measured temperature.
+func (d *Device) Temperature() float32 {
+	return d.temperature
+}
+
+// Humidity returns the last measured humidity.
+func (d *Device) Humidity() float32 {
+	return d.humidity
+}

dht20/registers.go

@@ -0,0 +1,6 @@
+package dht20
+
+// Constants/addresses used for I2C.
+
+// The I2C address which this device listens to.
+const defaultAddress = 0x38